^^ Well I was a Q3 player and I do pretty good in COD2 - for a casual gamer my stats are better than 90% of the kids that play non stop all the time, the so called pro gamers.
It is NOT VICE versa by any means. A good Q3 player has above decent performance in any FPS, while the latter is literally pathetic in Q3. Maybe your skills are average and that's not your point of view, but I know many quality Q3 players that totally own not only in Q3 but in every other FPS then get into. Q3 requires a lot of tactic and tracing opponents psyche all the time, plus it is really encouraging extremes when it comes to reflexes. Let me put it this way - IF YOU CAN DRIVE WELL AT 150 MPH you can also drive at 50 MPH, but good performance at 50 MPH does not guarantee the same performance at 150 MPH. It is that simple - quake 3 is demanding and it can take quite the skill, that's why between 2 players that are close in skill can still result in a tremendous difference in the end score. While in other games you are limited by the engine, resulting in a bottleneck for gaming performance. You are not as good as you are, but as good as the engine allows you. In Q3 the only bottleneck is the player himself.
http://www.youtube.com/watch?v=OiolB5OCyeU
I mean... if you ever played Q3 seriously - everything else is like slow motion for you, which makes things very very easy.